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vkd3d-shader/ir: Introduce a simple control flow graph structurizer.

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The structurizer is implemented along the lines of what is usually called
the "structured program theorem": the control flow is completely
virtualized by mean of an additional TEMP register which stores the
block index which is currently running. The whole program is then
converted to a huge switch construction enclosed in a loop, executing
at each iteration the appropriate block and updating the register
depending on block jump instruction.

The algorithm's generality is also its major weakness: it accepts any
input program, even if its CFG is not reducible, but the output
program lacks any useful convergence information. It satisfies the
letter of the SPIR-V requirements, but it is expected that it will
be very inefficient to run on a GPU (unless a downstream compiler is
able to devirtualize the control flow and do a proper convergence
analysis pass). The algorithm is however very simple, and good enough
to at least pass tests, enabling further development. A better
alternative is expected to be upstreamed incrementally.

Side note: the structured program theorem is often called the
Böhm-Jacopini theorem; Böhm and Jacopini did indeed prove a variation
of it, but their algorithm is different from what is commontly attributed
to them and implemented here, so I opted for not using their name.
This commit is contained in:
Giovanni Mascellani
2024-01-16 23:56:43 +01:00
committed by Alexandre Julliard
parent 19aef21369
commit 51f13391e6
Notes: Alexandre Julliard 2024-02-06 23:42:19 +01:00 
Approved-by: Giovanni Mascellani (@giomasce)
Approved-by: Conor McCarthy (@cmccarthy)
Approved-by: Henri Verbeet (@hverbeet)
Approved-by: Alexandre Julliard (@julliard)
Merge-Request: https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/607
8 changed files with 209 additions and 68 deletions
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147
libs/vkd3d-shader/ir.c
View File

@@ -470,6 +470,25 @@ static void dst_param_init_ssa_bool(struct vkd3d_shader_dst_param *dst, unsigned
dst->reg.idx[0].offset = idx;
}
static void dst_param_init_temp_uint(struct vkd3d_shader_dst_param *dst, unsigned int idx)
{
vsir_dst_param_init(dst, VKD3DSPR_TEMP, VKD3D_DATA_UINT, 1);
dst->reg.idx[0].offset = idx;
dst->write_mask = VKD3DSP_WRITEMASK_0;
}
static void src_param_init_temp_uint(struct vkd3d_shader_src_param *src, unsigned int idx)
{
vsir_src_param_init(src, VKD3DSPR_TEMP, VKD3D_DATA_UINT, 1);
src->reg.idx[0].offset = idx;
}
static void src_param_init_const_uint(struct vkd3d_shader_src_param *src, uint32_t value)
{
vsir_src_param_init(src, VKD3DSPR_IMMCONST, VKD3D_DATA_UINT, 0);
src->reg.u.immconst_u32[0] = value;
}
void vsir_instruction_init(struct vkd3d_shader_instruction *ins, const struct vkd3d_shader_location *location,
enum vkd3d_shader_opcode handler_idx)
{
@@ -2871,6 +2890,125 @@ fail:
return VKD3D_ERROR_OUT_OF_MEMORY;
}
static enum vkd3d_result simple_structurizer_run(struct vkd3d_shader_parser *parser)
{
const unsigned int block_temp_idx = parser->program.temp_count;
struct vkd3d_shader_instruction *instructions = NULL;
const struct vkd3d_shader_location no_loc = {0};
size_t ins_capacity = 0, ins_count = 0, i;
bool first_label_found = false;
if (!reserve_instructions(&instructions, &ins_capacity, parser->program.instructions.count))
goto fail;
for (i = 0; i < parser->program.instructions.count; ++i)
{
struct vkd3d_shader_instruction *ins = &parser->program.instructions.elements[i];
switch (ins->handler_idx)
{
case VKD3DSIH_PHI:
case VKD3DSIH_SWITCH_MONOLITHIC:
vkd3d_unreachable();
case VKD3DSIH_LABEL:
if (!reserve_instructions(&instructions, &ins_capacity, ins_count + 4))
goto fail;
if (!first_label_found)
{
first_label_found = true;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_MOV, 1, 1))
goto fail;
dst_param_init_temp_uint(&instructions[ins_count].dst[0], block_temp_idx);
src_param_init_const_uint(&instructions[ins_count].src[0], label_from_src_param(&ins->src[0]));
ins_count++;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_LOOP, 0, 0))
goto fail;
ins_count++;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_SWITCH, 0, 1))
goto fail;
src_param_init_temp_uint(&instructions[ins_count].src[0], block_temp_idx);
ins_count++;
}
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_CASE, 0, 1))
goto fail;
src_param_init_const_uint(&instructions[ins_count].src[0], label_from_src_param(&ins->src[0]));
ins_count++;
break;
case VKD3DSIH_BRANCH:
if (!reserve_instructions(&instructions, &ins_capacity, ins_count + 2))
goto fail;
if (vsir_register_is_label(&ins->src[0].reg))
{
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_MOV, 1, 1))
goto fail;
dst_param_init_temp_uint(&instructions[ins_count].dst[0], block_temp_idx);
src_param_init_const_uint(&instructions[ins_count].src[0], label_from_src_param(&ins->src[0]));
ins_count++;
}
else
{
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_MOVC, 1, 3))
goto fail;
dst_param_init_temp_uint(&instructions[ins_count].dst[0], block_temp_idx);
instructions[ins_count].src[0] = ins->src[0];
src_param_init_const_uint(&instructions[ins_count].src[1], label_from_src_param(&ins->src[1]));
src_param_init_const_uint(&instructions[ins_count].src[2], label_from_src_param(&ins->src[2]));
ins_count++;
}
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_BREAK, 0, 0))
goto fail;
ins_count++;
break;
case VKD3DSIH_RET:
default:
if (!reserve_instructions(&instructions, &ins_capacity, ins_count + 1))
goto fail;
instructions[ins_count++] = *ins;
break;
}
}
assert(first_label_found);
if (!reserve_instructions(&instructions, &ins_capacity, ins_count + 3))
goto fail;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_ENDSWITCH, 0, 0))
goto fail;
ins_count++;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_ENDLOOP, 0, 0))
goto fail;
ins_count++;
if (!vsir_instruction_init_with_params(&parser->program, &instructions[ins_count], &no_loc, VKD3DSIH_RET, 0, 0))
goto fail;
ins_count++;
vkd3d_free(parser->program.instructions.elements);
parser->program.instructions.elements = instructions;
parser->program.instructions.capacity = ins_capacity;
parser->program.instructions.count = ins_count;
parser->program.temp_count += 1;
return VKD3D_OK;
fail:
vkd3d_free(instructions);
return VKD3D_ERROR_OUT_OF_MEMORY;
}
enum vkd3d_result vkd3d_shader_normalise(struct vkd3d_shader_parser *parser,
const struct vkd3d_shader_compile_info *compile_info)
{
@@ -2889,6 +3027,9 @@ enum vkd3d_result vkd3d_shader_normalise(struct vkd3d_shader_parser *parser,
if ((result = materialize_ssas_to_temps(parser)) < 0)
return result;
if ((result = simple_structurizer_run(parser)) < 0)
return result;
}
else
{
@@ -2916,13 +3057,13 @@ enum vkd3d_result vkd3d_shader_normalise(struct vkd3d_shader_parser *parser,
remove_dead_code(&parser->program);
if ((result = flatten_control_flow_constructs(parser)) < 0)
return result;
if ((result = normalise_combined_samplers(parser)) < 0)
return result;
}
if ((result = flatten_control_flow_constructs(parser)) < 0)
return result;
if (TRACE_ON())
vkd3d_shader_trace(&parser->program);